Hardener for epoxy resin and epoxy resin composition

ABSTRACT

A curing agent for epoxy resins, the curing agent containing as an active ingredient a compound represented by the formula (1) or a salt thereof and an amine compound or a salt thereof, the curing agent being characterized in that at least one of the compound represented by the formula (1) and the amine compound is a salt of thiocyanic acid; and an epoxy resin composition having the curing agent incorporated therein: 
     
       
         NH 2 N(R 1 )(R 2 )  (1) 
       
     
     wherein R 1  and R 2  are the same or different and each represents alkyl having 1 to 8 carbon atoms, aryl, a nitrogen-containing heterocyclic group or when taken together, represents alkylene having 2 to 11 carbon atoms or a group represented by —R 3 —R 4 —R 5 — wherein R 3  and R 5  are the same or different and each represents alkylene having 1 to 8 carbon atoms, and R 4  is an oxygen atom, a sulfur atom or a group ═NR 6  or ═NNH 2 , wherein R 6  is a hydrogen atom or alkyl having 1 to 8 carbon atoms.

This application is the National Stage in the U.S. of PCT/JP00/07226filed Oct. 18, 2000.

TECHNICAL FIELD

The present invention relates to a curing agent for epoxy resin andepoxy resin composition.

BACKGROUND ART

Epoxy resin is widely used as sealing material, coating composition,adhesive, casting material, etc, in a variety of fields such aselectricity, electronics, and civil engineering and construction,because a cured product of epoxy resin has excellent electricalinsulating properties, moisture proof, heat resistance, solderingresistance, chemical resistance, durability, adhesive property, andmechanical strength. However, in case of mixing a filler to the epoxyresin, the mixture sometimes has a high viscosity which causes a problemdepending on use. In these cases, an organic solvent is usually added tothe mixture to reduce the viscosity.

Conventionally, the curing of epoxy resin is carried out by adding acuring agent to epoxy resin, followed by heating. As typicalrepresentative examples of curing agent, there are, for example,diethylenetriamine, triethylenetetramine, isophoronediamine,diaminodiphenylmethane, diaminodiphenylsulfone, polyamides,dicyandiamide, hexahydrophthalic anhydride, methyl nadic anhydride,novolac type phenol resin, tertiary amines, imidazoles, and aminecomplex of boron trifluoride.

Of these curing agents, ones which can cure epoxy resin at roomtemperature are amine curing agents such as diethylenetriamine,triethylenetetramine, polyamides, and tertiary amines. However, thesecuring agents require a long time of four to seven days for curing. Itis difficult for other curing agents to be cured at room temperature,and they generally require a curing temperature of 80 to 200° C., and acuring time of 0.5 to 6 hours.

Meanwhile, an epoxy resin adhesive for outdoor construction is generallyused in the field of civil engineering and construction. With aconventional curing agent, however, it is very difficult to cure epoxyresin without heating, as previously described. Even with one capable ofcuring, it takes an extremely long period of time, namely, four to sevendays. Especially, for winter-season execution of works in which theoutdoor temperature is often 10° C. and below, it is essential toinitiate the curing reaction by heating.

Such characteristic of epoxy resin adhesive prolongs the period ofexecution of works in civil engineering and construction, which is alsoone of the causes of interfering with labor saving.

Further, most of conventional curing agents for epoxy resin haveproblems that curing ability decreases with the presence of water, along time is required for curing, characteristics of cured product aregreatly impaired, or cured product is not obtained. Therefore, in fact,use of curing agent is greatly limited in outdoor under rain or inshore-protection works.

As means for overcoming such problems, the present inventors proposedcompounds represented by the formula (1), typically 1-aminopyrrolidine,as a curing agent for epoxy resins which agent can quickly cure an epoxyresin even at room temperature or at a low temperature without loweringthe curability in the presence of water (Japanese Patent ApplicationNos. 137743/1998 and 285932/1998).

These compounds are excellent in curability in a low temperature rangecompared with conventional curing agents for epoxy resins. However, thecured epoxy resin is insufficient in water resistance immediately aftercuring, and takes a long time (aging for about 48 hours) until the curedproduct becomes satisfactory in water resistance. Consequently, there isa need for further reducing such aging period in order to shorten theterm of construction works.

In recent years, a demand exists for materials which are safe andoutstanding in resource-saving capability and in environmentalconservation. There is a growing interest in using aqueous solvents inplace of organic solvents for diluting purposes in view of control ofvolatile organic compounds (VOC) concerning the discharge of solvents.Especially the concern for this matter is positive in the fields ofcoating compositions and adhesive agents. In such applications, thecuring agents are mostly used in situations where people are living.Accordingly, it is important that the curing agents scarcely smell,assure safety against a fire, explosion and the like and take only ashort period until completion of operation. In this background, epoxyresin emulsions are increasingly used as a substitute, since theemulsions contain little or no volatile organic solvent, preventenvironmental pollution, and are excellent in safety and hygiene and inpreventive effect against fire hazards.

In preparing an epoxy resin emulsion, generally an epoxy resin is madehydrophilic with an emulsifier and is dispersed in an aqueous solvent.The epoxy resin emulsion, when used, is cured with a curing agent.Mostly conventional per se known curing agents for epoxy resin emulsionsare made hydrophilic with an emulsifier and dispersed in an aqueoussolvent. For this reason, the curing agent poses problems of reducingthe curability, requiring a prolonged period of time in curing, andseriously degrading the properties of cured product.

Known as commercial aqueous products of epoxy resins are, for example,epoxy resin emulsions available under the trade name EPI-REZ seriesmanufactured by Yuka Shell Epoxy Co., Ltd. Known curing agents include,for example, those available under the trade name Epicure series(polyamideamine adduct or the like) manufactured by Yuka Shell EpoxyCo., Ltd. However, the above- mentioned curing agents retard curing atroom temperature and take a long period of time in curing.

An object of the present invention is to provide a curing agent forepoxy resins which can quickly cure the epoxy resin in a low temperaturerange and which imparts water resistance to a cured product in a shorttime, and an epoxy resin composition containing the curing agent.

Another object of the invention is to provide a curable epoxy resinemulsion composition which is quickly curable at room temperature.

DISCLOSURE OF THE INVENTION

The present invention provides a curing agent for epoxy resins, thecuring agent containing as an active ingredient a compound representedby the formula (1) or a salt thereof and an amine compound or a saltthereof, the curing agent being characterized in that at least one ofthe compound represented by the formula (1) and the amine compound is asalt of thiocyanic acid:

NH₂N(R¹)(R²)  (1)

wherein R¹ and R² are the same or different and each represents alkylhaving 1 to 8 carbon atoms, aryl, a nitrogen-containing heterocyclicgroup or when taken together, represents alkylene having 2 to 11 carbonatoms or a group represented by —R³—R⁴—R⁵— wherein R³ and R⁵ are thesame or different and each represents alkylene having 1 to 8 carbonatoms, and R⁴ is an oxygen atom, a sulfur atom or a group ═NR⁶ or ═NNH²,wherein R⁶ is a hydrogen atom or alkyl having 1 to 8 carbon atoms.

The present invention also provides an epoxy resin composition whichcomprises an epoxy resin and the curing agent for epoxy resins asdefined in claim 1.

The present invention further provides an epoxy resin emulsioncomposition which comprises an epoxy resin emulsion and a compoundrepresented by the formula (1) or a salt thereof.

The curing agent for epoxy resins according to the invention can quicklycure the epoxy resin at room temperature or in a lower temperaturerange, or even at a temperature as low as −20° C. although depending onthe case. Consequently, for example, even if an epoxy resin adhesiveagent for outdoor use is used in a construction work, the adhesive agentcan be cured without heating by use of the curing agent for epoxy resinsaccording to the invention, whereby great benefit is brought to theconstruction works. Further, construction work using an epoxy resin incold climate can be easily and quickly performed by using the curingagent of the invention.

The curing agent for epoxy resins according to the present inventioncontains as an active ingredient a compound represented by the formula(1) or a salt thereof:

NH₂N(R¹)(R²)  (1)

wherein R¹ and R² are the same or different and each represents alkylhaving 1 to 8 carbon atoms, aryl, a nitrogen-containing heterocyclicgroup or when taken together, represents alkylene having 2 to 11 carbonatoms or a group represented by —R³—R⁴—R⁵— wherein R³ and R⁵ are thesame or different and each represents alkylene having 1 to 8 carbonatoms, and R⁴ is an oxygen atom, a sulfur atom or a group ═NR⁶ or ═NNH₂,wherein R⁶ is a hydrogen atom or alkyl having 1 to 8 carbon atoms.

Examples of alkyl having 1 to 8 carbon atoms are methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, s-butyl, n-pentyl,isopentyl, t-pentyl, neopentyl, n-hexyl, isohexyl, heptyl, and octyl.Examples of alkylene having 2 to 11 carbon atoms are ethylene,propylene, butylene, hexylene, octylene, decamethylene, andundecamethylene. Examples of alkylene having 1 to 8 carbon atoms aremethylene, ethylene, propylene, butylene, hexylene, and octylene.Examples of aryl are phenyl, tolyl, and naphthyl. Examples ofnitrogen-containing heterocyclic group are pyridyl, piperidinyl, andpyrazolyl.

Specific examples of the compound represented by the formula (1) are1-aminopyrrolidine (1-AP), 1-aminopiperidine, 1-aminohomorpiperidine(AHP), 1-aminopiperazine, N-amino-N′-methylpiperazine (AMPI),N-aminomorpholine (AMP), N-aminothiomorpholine, 1,1-dimethylhydrazine(UDMH), 1,1-diethylhydrazine, 1,1-dipropylhydrazine,1,1-dibutylhydrazine, monomethylhydrazine, monoethylhydrazine,monopropylhydrazine, monoisopropylhydrazine, monobutylhydrazine,mono-tert-butylhydrazine, 1-ethyl-1-methylhydrazine,1-methyl-1-propylhydrazine, 1-butyl-1-methylhydrazine,1-methyl-1-phenylhydrazine, 1,1-diphenylhydrazine, monophenylhydrazine,and 2-hydrazinopyridine.

Among these compounds, especially preferred are those represented by thefollowing formulas, namely 1-aminopyrrolidine (1-AP),1-aminohomopiperidine (AHP), N-amino-N′-methylpiperazine (AMPI), andN-aminomorpholine (AMP):

Salts of these compounds include, for example, thiocyanate, borate,hydrochloride, phosphate, and sulfate. Thiocyanate, if used, needs to beemployed in combination with an amine compound or a salt thereof to bedescribed later.

The compound of the formula (1) or a salt thereof to be used in thepresent invention can be used as it is, or in the form of powder,liquid, an aqueous solution, an organic solvent solution, or adispersion. Examples of useful organic solvents are lower alcohols suchas methanol, ethanol and isopropanol; aromatic hydrocarbons such astoluene and xylene; aliphatic hydrocarbons such as hexane; ethers; polarsolvents; and halogenated hydrocarbons. Optionally a solution or adispersion of the compound in water or in a proper organic solvent maybe used.

Examples of the amine compound which is used as at least one of thecompound of the formula (1) or a salt thereof and the amine compound ora salt thereof which is a salt of thiocyanic acid are alkylamine, linearaliphatic amine, cyclic amine, aromatic amine, aliphatic aromatic amine,epoxy-modified products thereof, Mannich modified products thereof, andMichael modified addition products thereof.

Useful alkylamines include, for example, compounds represented by theformula NH₂(R⁷) (wherein R⁷ is a straight chain or branched chain alkylhaving 1 to 12 carbon atoms) such as methylamine, ethylamine,propylamine, isopropylamine, butylamine, sec-butylamine, t-butylamine,n-octylamine, and 2-ethylhexylamine; compounds represented by theformula NH(R⁸) (R⁹) (wherein R⁸ and R⁹ are the same or different andeach represents a straight chain or branched chain alkyl having 1 to 12carbon atoms) such as dimethylamine, diethylamine, dipropylamine,diisopropylamine, dibutylamine, di-sec-butylamine, di-t-butylamine,di-n-octylamine, and di-2-ethylhexylamine; compounds represented by theformula N(R¹⁰) (R¹¹) (R¹²) (wherein R¹⁰, R¹¹ and R¹² are the same ordifferent and each represents a straight chain or branched chain alkylhaving 1 to 12 carbon atoms) such as trimethylamine, tripropylamine,triisopropylamine, tributylamine, tri-sec-butylamine, tri-t-butylamine,and tri-n-octylamine.

Examples of linear aliphatic amines are compounds represented by theformula (R¹³) (R¹⁴)N(CH₂)nN(R¹⁵) (R¹⁶) (wherein R¹³, R¹⁴, R¹⁵, and R¹⁶are the same or different and each represents a hydrogen atom, orstraight chain or branched chain alkyl having 1 to 6 carbon atoms and nis a number from 1 to 5) such as 3-(dimethylamino) propylamine,3-(diethylamino)-propylamine, 3-(methylamino) propylamine,3-(dibutylamino)propylamine, and tetramethyl-ethylenediamine; compoundsrepresented by the formula N(R¹⁷) (R¹⁸) (CH₂)nNH₂ (wherein R¹⁷ and R¹⁸are the same or different and each represents a hydrogen atom, orstraight chain or branched chain alkyl having 1 to 6 carbon atoms and nis a number from 1 to 5) such as ethylenediamine; compounds representedby the formula N(R¹⁹) [(CH₂)nNH₂])₂ (wherein R¹⁹ is a hydrogen atom, orstraight chain or branched chain alkyl having 1 to 6 carbon atoms and nis a number from 1 to 5) such as 3,3′-iminobis(propylamine) andN-methyl-3,3′-iminobis(propylamine); compounds represented by theformula N[(CH₂)nNH₂]₃ (wherein n is a number from 1 to 5) such astris(2-aminoethyl)amine; compounds represented by the formulaNH₂(CH₂)m[(CH₂)nNH]xNH₂ (wherein m, n and x represent a number from 1 to5) such as diethylenetriamine, triethylenetetramine,tetraethylenepentamine, and other linear aliphatic amines such as3-(2-ethylhexyloxy)propylamine, 3-ethoxypropylamine,3-methoxypropylamine, allylamine, diallylamine, triallylamine,polyoxypropylenediamine, and polyoxypropylenetriamine.

Examples of cyclic amines are bis(4-amino-3-methyldicyclohexyl) methane,diaminodicyclohexylmethane, bis(aminomethyl)cyclohexane,N-aminoethylpyrazine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro(5,5)undecane, m-xylenediamine,isophoronediamine, menthenediamine, 1,4-bis(2-amino-2-methylpropyl)piperazine, N,N′-dimethylpiperazine, pyridine, picoline,1,8-diazabicyclo[5,4,0]-7-undecene, benzylmethylamine,2,4,6-tris(dimethylaminomethyl)phenol, 2-(dimethylaminomethyl)-phenol,2-methylimidazole, and 2-ethyl-4-methylimidazole.

Examples of aromatic amines are metaphenylenediamine,diaminodiphenylmethane, diaminodiphenylsulfine, diaminodiethyldimethyldiphenylmethane, and α, α′,-bis(4-aminophenyl) -p-diisopropylbenzene.

Examples of aliphatic aromatic amines are α-(m/p-aminophenyl) ethylamineand the like.

Examples of salts of these amine compounds are thiocyanate, borate,hydrochloride, phosphate, and sulfate. Among them, preferred specificexamples of thiocyanates are diethylenetriamine thiocyanate (DATA.SCN),2,4,6-tris(dimethylaminomethyl)phenol thiocyanate (DMP-30.SCN),1,8-diazabicyclo[5.4.0]-7-undecene thiocyanate (DBU.SCN),m-xylenediamine thiocyanate (MXDA.SCN), and isophoronediaminethiocyanate (IPDA SCN).

The compound represented by the formula (1) or a salt thereof and theamine compound and a salt thereof, at least one of which is a salt ofthiocyanic acid in the curing agent, can be used as a mixture, or can beused in the form of an aqueous solution, an organic solvent solution ora dispersion. Examples of useful organic solvents are lower alcoholssuch as methanol, ethanol and isopropanol; aromatic hydrocarbons such astoluene and xylene; aliphatic hydrocarbons such as hexane; ethers; polarsolvents; and halogenated hydrocarbons. Optionally a solution or adispersion of the compound in water and in a proper organic solvent maybe used. Among these, an aqueous solution is particularly preferable.

The compound represented by the formula (1) or a salt thereof and theamine compound and a salt thereof in the curing agent are used in amolar ratio of the former to the latter of, e.g. from approximately 1:10to 10:1.

Of the active ingredients in the curing agent for epoxy resins asdefined in claim 1, at least one of the compound represented by theformula (1) and the amine compound is essentially a salt of thiocyanicacid.

The curing agent for epoxy resins as defined in claim 1 can quickly curethe epoxy resin when used in the presence of water. When the curingagent is used in the presence of water, water is used preferably in amolar ratio of water:compound of the formula (1) of from 0.8:1 to 1.2:1.

The curing agent in which at least one of the compound represented bythe formula (1) or a salt thereof and the amine compound or a saltthereof is a salt of thiocyanic acid can quickly cure the epoxy resineven at room temperature and can impart improved water resistance andtoughness to the cured epoxy resin when used as a curing agent for epoxyresin emulsion.

Epoxy resin which can be used in the invention is not specificallylimited, and various epoxy resins are usable. Examples thereof areglycidyl ether type epoxy resin, glycidyl ester resin and glycidylaminetype epoxy resin.

Examples of glycidyl ether type epoxy resin are bisphenol A type,bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol Atype, bisphenol S type, bisphenol AF type, biphenyl type, naphthalenetype, fluorene type, phenol novolac type, cresol novolac type, DPPnovolac type, trifunctional type, tris(hydroxyphenyl)methane type, andtetraphenylolethane type epoxy resins.

Examples of glycidyl ester type epoxy resin are hexahydrophthalate typeand phthalate type epoxy resins.

Examples of glycidylamine type epoxy resin aretetraglycidyldiaminodiphenylmethane, triglycidyl isocyanurate, hydantointype, 1,3-bis (N,N-diglycidylaminomethyl) cyclohexane, aminophenol type,aniline type, and toluidine type epoxy resins.

The epoxy resin emulsion composition of the present invention comprises(i) an epoxy resin which is made hydrophilic with an emulsifier such asa surfactant, and is thereby dispersed in an aqueous solvent; and (ii)the compound of the formula (1) or a salt thereof as a curing agent forepoxy resins. The curing agent for epoxy resins according to theinvention contains the compound represented by the formula (1) or a saltthereof and the amine compound or a salt thereof in which at least oneof the compound represented by the formula (1) and the amine compound isa salt of thiocyanic acid.

The epoxy resin emulsion composition of the present invention containingan epoxy resin at a high concentration exhibits a lower degree ofincrease in viscosity than when an organic solvent is used.Consequently, the above-mentioned composition is easy to apply in acoating operation. Further the foregoing composition, because of anaqueous solvent used, can adhere well to a wet substrate surface, andmay contain a hydraulic material (such as gypsum and Portland cement) asa filler. The composition which contains little or no organic solvent isusable in a closed tank or chamber and is excellent in preventive effectagainst environmental pollution. With such outstanding features, thecomposition can be widely used for coating compositions or adhesivematerials.

The most remarkable features of the composition according to theinvention are that it can overcome the defect of conventional epoxyresin emulsions in respect of the curing rate, and that it can cure theepoxy resin quickly or in a short time, of course, at a high temperatureand at room temperature or lower, e.g. at a temperature as low as 5° C.Especially when the curing agent to be used contains the compound of theformula (1) or a salt thereof and the amine compound and a salt thereofin which at least one of the compound of the formula (1) and the aminecompound is a salt of thiocyanic acid, surprisingly the cured product isimparted high water resistance and good mechanical properties such asfilm strength which conventional epoxy resin emulsions disadvangeouslylack.

Emulsifiers useful in the invention are not specifically limited andinclude various emulsifying agents. Examples of anionic emulsifiers aresodium lauryl sulfate and like sulfuric acid ester salts of higheralcohols, alkylbenzene sulfonate, alkylnaphthalene sulfonate,dialkylsulfosuccinic acid salt, and polyoxyethylene ether sulfate.Examples of nonionic emulsifiers are polyoxyethylene alkyl ether,polyoxyethylene alkylphenol ether, polyoxyethylene sorbitan fatty acidester, sorbitan fatty acid ester, polyoxyethylene acyl ester,oxyethylene-oxypropylene block copolymer, and fatty acid monoglyceride.These anionic and nonionic emulsifiers can each be used singly or inmixture of at least two of them.

It is desirable to carry out a phase inversion emulsification method inproducing an epoxy resin emulsion. First, a small amount of water ismixed with an emulsifier-containing oil component (epoxyresin-containing organic solvent) to give a W/O type emulsion. Then,small amounts of water are gradually added to bring about phaseinversion, eventually giving an O/W type emulsion.

Mixing devices include, for example, an axis-type agitators havingrotating blades, homogenizers, homomixers, and colloid mills. Anemulsification temperature is in the range of, preferably 10 to 80° C.,more preferably 30 to 50° C.

There is no specific limitation on the average particle size ofparticles in the epoxy resin emulsion. Usually the particle size thereofis about 0.01 to about 10 μm, preferably about 0.1 to about 1 μm. If theaverage particle size of particles exceeds 10 μm, precipitation islikely to occur, resulting in instability.

The amount of the emulsifier used is preferably 100 parts by weight orless, more preferably 5 to 20 parts by weight, per 100 parts by weightof the epoxy resin.

Specific examples of the epoxy resin emulsion include EPI-REZ aqueousepoxy resin series manufactured by Yuka Shell Co., Ltd. such as 3510W60,3515W60, 3519W50, 3520WY55, 3540WY55, 3551WY43, 5522WY55, and 6006W70.Also available are ADEKA RESIN aqueous epoxy resin series manufacturedby Asahi Denka Kogyo Co., Ltd- such as EM-0512, EM-0517, and EM-101-50.These epoxy resin emulsions can be used either alone or in combination.

The epoxy resin emulsion composition of the present invention containsthe compound of the formula (1) or a salt thereof as the curing agentfor epoxy resins. Further, the compound of the formula (1) or a saltthereof and the amine compound and a salt thereof in which at least oneof the compound of the formula (1) and the amine compound is a salt ofthiocyanic acid can be used as the curing agent.

The curing agent of the invention is soluble in water, and thereforeeliminates the need to make the epoxy resin hydrophilic with anemulsifier such as a surfactant. Consequently the curing agent isexcellent in workability and the cured product thus obtained is scarcelydegraded in properties due to the emulsifier and is excellent in waterresistance and film strength especially when used in a coatingcomposition.

The proportions of the curing agent of the invention and the epoxy resinor epoxy resin emulsion (solid content) are not specifically limited andare selectable from a wide range depending on the type of the epoxyresin, type and amount of other additives used, purpose of the curedepoxy resin, curing conditions (predetermined curing time, curingtemperature, curing location and the like). Usually the proportions areso determined that the equivalent ratio of epoxy group/amine groupranges from about 0.5 to about 2, preferably from about 0.7 to about 1.2in which case the calculation of equivalent ratio is made between theepoxy group in the epoxy resin and the total of amine groups in thecompound of the formula (1) and in the amine compound.

The epoxy resin or epoxy resin emulsion composition according to theinvention may contain a conventional curing agent and a conventionalcuring accelerator within the range which does not adversely affecttheir preferred properties. Examples of the curing agent which can beadded are diethylenetriamine, triethylenetetramine, isophoronediamine,diaminodiphenylmethane, diaminodiphenylsulfone, polyamide,dicyandiamide, hexahydrophthalic anhydride, methylnadic anhydride,novolak phenolic resin, tertiary amines, imidazoles, boron trifluorideand like amine complexes, melamine, methylolmelamine, and resolcompounds. Examples of the curing accelerator are tri-n-butylamine,benzylmethylamine, 2,4,6-tris (dimethylaminomethyl)phenol and liketertiary amines, 2-methylimidazoles, 2-ethylimidazoles,2-ethyl-4-methylimidazole, 2-phenylimidazole, and like imidazoles. Thesecuring agents and curing accelerators can be used either alone or incombination.

To epoxy resin or epoxy emulsion composition can be added, as required,a filler and reinforcing agent, which have conventionally been added toepoxy resin. Examples of fillers are silica, fused quartz, calciumcarbonate, barium carbonate, barium sulfate, alumina hydrate, alumina,magnesia hydrate, zircon, cordierite, silicon nitride, boron nitride,and aluminum nitride. Examples of reinforcing agents are talc, mica,glass fiber, potassium titanate fiber, titanium dioxide fiber,wallastonite, xonotlite, zinc silicate fiber, aramide fiber, carbonfiber and boron fiber. It is possible to suitably change the kind,amount or the like of a filler and reinforcing agent in order to obtaindesired properties of a cured epoxy resin product. Usually, it issuitable to add about 20 to 160 parts by weight of a filler andreinforcing agent, preferably about 50 to 120 parts by weight, based on100 parts by weight of epoxy resin. Filler and reinforcing agent may beused singly or in a combination of at least two of them.

Further, various additives may be added as required to the above epoxyresin or epoxy emulsion composition. Examples of such additives arepigment (particulate titanium dioxide, carbon black, red iron oxide,yellow iron oxide, etc.), viscosity adjusting agent, leveling agent,antifoamer, coupling agent, plasticizer, diluent, flame retardant(magnesium hydroxide, aluminum hydroxide, antimony oxide, alkylphosphates or phosphazenes), and organic solvent.

The epoxy resin composition of the invention is applicable to coat,bond, or repair materials such as metal, synthetic resin, cement,ceramics, knitting or fabric of inorganic or organic fiber (glass cross,etc.) and papers, or to prepare a shaped product using the composition.Specifically, an article of various shape may be dipped in the epoxyresin composition, alternatively, the epoxy resin composition is appliedor coated to the article surface, or poured into the article or filledinto opening between articles, and then allowed to stand as it is, forcuring. When curing, heating is not required particularly, but it ispossible to heat to about 40 to 120° C. as required depending on thecomposition.

Also, the above epoxy resin composition can be formed into a shapedproduct of a desired shape, in accordance with the usual molding method,e.g., casting molding and injection molding.

BEST MODE OF CARRYING OUT THE INVENTION

The present invention is described below in more detail with referenceto the following examples to which, however, the invention is notlimited at all.

EXAMPLES 1 TO 5

To 10 g of an epoxy resin (Epikote 806, product of Yuka Shell Epoxy Co.,Ltd., epoxy equivalent 165) were added 0.94 g of a 83% aqueous solutionof 1-aminopyrrolidine (curing agent), and 0.82 g of each compound(additive) shown in Table 1. Then, the three substances were mixed. Themixture was placed into an aluminum cup 5 cm in diameter to a thicknessof 1 cm and was aged for 24 hours.

In 24 hours, the obtained cured product was subjected to a 24-hour waterabsorption test to measure an absorption ratio. The results are shown inTable 1. In the procedure, the addition, mixing, curing and absorptiontest were all carried out at 5° C.

Comparative Example 1

A test was conducted in the same manner as in Example 1 except that athiocyanate of amine compound was not added. The results are shown inTable 1.

Comparative Examples 2 and 3

A test was conducted in the same manner as in Example 1 except thatsodium thiocyanate or ammonium thiocyanate was used as an additive. Theresults are shown in Table 1.

EXAMPLES 6 and 7

To 10 g of an epoxy resin (Epikote 806, epoxy equivalent 165) were added1.3 of 1-aminopyrrolidine thiocyanate (AP SCN, curing agent), and 0.7 gof each compound (additive) shown in Table 2. Then, the three substanceswere mixed. The mixture was placed into an aluminum cup 5 cm in diameterto a thickness of 1 cm and was aged for 24 hours.

In 24 hours, the obtained cured product was subjected to a 24-hour waterabsorption test to measure an absorption ratio. The results are shown inTable 2.

Comparative Example 4

A test was conducted in the same manner as in Example 2 except that anadditive was not added. The results are shown in Table 2.

TABLE 1 Amount (g) Water Epikote curing Cure state absorption Additive806 agent Additive after 24 hr ratio (%) Ex. 1 DETA · SCN 10 0.94 0.82cure 0.4 Ex. 2 DMP-30 · SCN 10 0.94 0.82 cure 0.7 Ex. 3 DBU · SCN 100.94 0.82 cure 0.5 Ex. 4 MXDA · SCN 10 0.94 0.82 cure 0.4 Ex. 5 IPDA ·SCN 10 0.94 0.82 cure 0.4 Com. Ex. 1   — 10 0.94 0 cure 1.7 Com. Ex. 2Sodium 10 0.94 0.82 non-cure — thiocyanate Com. Ex. 3 Ammonium 10 0.940.82 non-cure — thiocyanate

TABLE 2 Amount (g) Water Epikote AP · Cure state absorption Additive 806SCN Additive after 24 hr ratio (%) Ex. 6 DETA 10 1.3 0.7 cure 0.3 Ex. 7MXDA 10 1.3 0.7 cure 0.2 Com. — 10 1.3 0.7 non-cure — Ex. 4

EXAMPLES 8 and 9

A bisphenol A epoxy resin emulsion shown in Table 3 and a 83% aqueoussolution of 1-aminopyrrolidine (1-AP) were used in an equivalent ratioof amine group/epoxy group of 0.2. The two substances were mixedtogether and applied to a steel plate (0.8 mm in thickness) to athickness of 0.3 mm to produce a test piece.

A test for the curing rate was conducted at room temperature (20° C.)according to JIS K 5400. The results are shown in Table 3. The term“drying to the touch” indicates a period of time taken until the coatingcomposition did not adhere to the finger when touched by the finger. Theterm “dry hard” indicates a period of time taken until a finger printwas not left on the coating film when the finger was pressed on thecoating film. “EPI-REZ 3520 WY55” (hereinafter referred to as “EP-1”):

Manufactured by Yuka Shell Epoxy Co., Ltd., bisphenol A type epoxy resinemulsion, solid content 55%, epoxy equivalent 520 “EPI-REZ 5522 WY55”(hereinafter referred to as “EP-2”):

Manufactured by Yuka Shell Epoxy Co., Ltd., modified polyfunctionalbisphenol A type epoxy resin emulsion, solid content 53%, epoxyequivalent 625

TABLE 3 epoxy resin Curing agent emulsion (wt. parts) (wt. parts) dryingto the dry hard EP-1 EP-2 1-AP touch (hr) (hr) Ex. 8 100 1.7 2 9 Ex. 9100 1.4 2 9

EXAMPLES 10 and 11

The same procedures as in Examples 8 and 9 were effected except that a94% aqueous solution of 1-aminopyrrolidine and m-xylenediaminethiocyanate (MXDA.SCN) were used as the curing agent in an equivalentratio of amine group/epoxy group of 0.9. The results are shown in Table4. 1-AP and MXDA.SCN were used in an equal molar ratio.

Comparative Examples 5 and 6

The same procedures as in Examples 8 and 9 were conducted except that anamideamine curing agent (manufactured by Yuka Shell Epoxy Co., Ltd.,trade name “Epicure 8536MY60”, solid content 60%, amine value 120mgKOH/g, hereinafter called “EH-11”) was used in a molar ratio of aminegroup/epoxy group of 1.0. The results are shown in Table 4.

In respect of Examples 10 and 11 and Comparative Examples 5 and 6, thetest pieces were aged at room temperature (20° C.) for a week accordingto JIS K5400, and then were subjected to a water resistance test and toa falling ball test.

TABLE 4 epoxy resin emulsion curing agent (wt. parts) (wt. parts) EP-1EP-2 1-AP + MXDA · SCN EH-1 Ex. 10 100 4.9 Ex. 11 100 4.9 Com. Ex. 5 10082.1 Com. Ex. 6 100 68.3 water resistance Falling drying to turn balltest the touch dry hard white swell peel (1.5 m) (hr) (hr) Ex. 10 ◯ ◯ ◯◯ 2 6.5 Ex. 11 ◯ ◯ ◯ ◯ 2 6.5 Com. Ex. 5 × ◯ ◯ × 6.5 26 Com. Ex. 6 × ◯ ◯× 6.5 26

The amounts of the epoxy resin emulsions and the amounts of the curingagents in Tables 3 and 4 are all expressed in part by weight.

Industrial Applicability

According to the present invention, there can be obtained a curing agentfor epoxy resins which can quickly cure the epoxy resin in a lowtemperature range and can give improved water resistance to the curedproduct in a short time.

The curing agent for epoxy resins according to the invention can quicklycure the epoxy resin at room temperature or in a lower temperaturerange, or even at a temperature as low as −20° C. although depending onthe case. Consequently, for example, even if an epoxy resin adhesiveagent for outdoor use is used in a construction work, the adhesive agentcan be cured without heating by use of the curing agent for epoxy resinsaccording to the invention, whereby great benefit is brought to theconstruction works. Further, construction works using an epoxy resin incold climate can be easily and quickly carried out.

According to the invention, there can be obtained a curable epoxy resinemulsion composition which contains little or no volatile organicsolvent, effectively prevents environmental pollution, and isoutstanding in safety and hygiene and in preventive effect against firehazards.

The epoxy resin emulsion composition of the invention can quickly curethe epoxy resin even at room temperature with or without heating andprovides the cured product with excellent properties.

What is claimed is:
 1. A curing agent for epoxy resins, the curing agentcontaining as an active ingredient a compound represented by the formula(1) or a salt thereof and an amine compound or a salt thereof, thecuring agent being characterized in that at least one of the compoundrepresented by the formula (1) and the amine compound is a salt ofthiocyanic acid: NH₂N(R¹)(R²)  (1) wherein R¹ and R² are the same ordifferent and each represents alkyl having 1 to 8 carbon atoms, aryl, anitrogen-containing heterocyclic group or when taken together,represents alkylene having 2 to 11 carbon atoms or a group representedby —R³—R⁴—R⁵— wherein R³ and R⁵ are the same or different and eachrepresents alkylene having 1 to 8 carbon atoms, and R⁴ is an oxygenatom, a sulfur atom or a group ═NR⁶ or ═NNH₂, wherein R⁶ is a hydrogenatom or alkyl having 1 to 8 carbon atoms.
 2. A curing agent for epoxyresins as defined in claim 1 wherein the compound represented by theformula (1) is 1-aminopyrrolidine.
 3. An epoxy resin composition whichcomprises an epoxy resin and the curing agent for epoxy resin ofclaim
 1. 4. An epoxy resin emulsion composition which a comprises anepoxy resin emulsion and the curing agent for epoxy resins of claim 1.5. An epoxy resin emulsion composition which comprises an epoxy resinemulsion and the compound represented by the formula (1) or a saltthereof.
 6. An epoxy resin composition which comprises an epoxy resinand the curing agent for epoxy resin of claim
 2. 7. An epoxy resinemulsion composition which comprises an epoxy resin emulsion and thecuring agent for epoxy resins of claim 2.